A 20-year-old man is accused of buying assault rifles and more than 400 rounds of ammunition in a plot to commit mass murder at a Twilight screening and a Missouri Walmart.

Blaec Lammers' plot was foiled because his mother alerted police, according to court documents.

The woman told police her son had bought weapons similar to those used by a gunman inside an Aurora, CO, movie theater showing the premiere of the latest Batman movie. Twelve people died and 58 were injured in Colorado.

"His mother further stated that, with the opening of the new Twilight movie, she was concerned that Blaec Lammers may have intentions of shooting people at the movie," according to the court documents.

After he was taken in for questioning, Lammers admitted he had bought the firearms with the intention of shooting up the movie theater in Bolivar on Sunday. However, he later decided to also target a Walmart because he feared running out of ammunition and he would have access to additional ammunition inside the Walmart, according to court documents.

He also had been practicing using the weapons at a nearby shooting range, according to court documents.

Lammers is being held on a $500,000 bond. He was charged Friday with first-degree assault, making a terroristic threat and armed criminal action.

The mother contacted police on Thursday. In 2009, Lammers claimed he wanted to fatally stab a Walmart employee and followed the employee around the store before he was contacted by officers, according to court documents.

Lammers was not convicted in state court in association with this. Before Friday, he had only faced speeding tickets.

"Blaec Lammers stated that he had a lot in common with the people involved in (recent mass shootings). Blaec Lammers stated that he was quiet, kind of a loner, had recently purchased firearms and didn't tell anybody about it, and had homicidal thoughts," according to court documents.

He then told officers he bought the assault weapons with the plans of killing people watching the Breaking Dawn Part 2 movie on Sunday, according to court documents. He had already purchased tickets and said, "he was going to shoot people at the movie theater on that night," according to court documents.

"So he decided that he would go and shoot people at Walmart in Bolivar," according to court documents. "Blaec Lammers stated that he would walk into the store and just start shooting people at random and if he ran out of ammunition . . . he would just break the glass where the ammunition is stored and get some more and keep on shooting until police arrived. Blaec Lammers then stated that he would then turn himself into police when they arrived."

One rifle was purchased on Monday while the second was bought on Tuesday. Court documents did not state where Lammers made the purchases.

Lammers said he had been to a shooting range in Aldrich to practice using the rifles.

"Blaec Lammers stated that he had never shot a gun before and wanted to make sure he knew how they functioned," according to court documents.

According to court documents, Lammers had stopped taking medication for a mental condition when he began plotting the mass killings.

Law enforcement officials and others have commended Lammers' mother for quickly contacting authorities about her concerns.

Those inside Lammers' home drove away Friday afternoon without comment to KCTV5.

Ashley Miller, who lives in a nearby town, told the Associated Press she has known Lammers for about a year and described him as "one of the sweetest guys I had ever met" but "very emotional," noting he would periodically stop talking to her.

She said he told her that he had bounced between relatives growing up. As an adult, he bounced between girlfriends, she said.

"He was never actually happy," she told the AP in a phone interview. "I think he had depression or something."

Neighbors of Lammers in Bolivar, which is in southwest Missouri near Springfield, said they were shocked and horrified by the allegations.

"It's shocking, especially when I have young kids, it's scary," one neighbor said.

They said they hope that Lammers will get the mental help he apparently needs.

"Wow, to think that this could happen in Bolivar, I mean jeez," Lori King said as she apologized for getting emotional.

King and her family had just left a Twilight screening.

"I raised three boys, and I have a granddaughter. It just terrifies me that something could happen to her," King said while fighting to hold back tears.

Law enforcement officials plan to ask a judge to require Lammers undergo a mental health evaluation.

Fred Guttenberg, the father of Jaime Guttenberg, one of the 17 killed last week in Parkland, FL, pressed Sen. Marco Rubio on the role of guns and assault weapons in the shooting during a CNN town hall event on Wednesday, Feb. 21. (Source: CNN)

Senator Marco Rubio faced a barrage of tough questioning related to gun control and the shooting at Marjory Stoneman Douglas High School in Florida at a CNN town hall event on Wednesday.